Ponatinib may cause a blood clot to form in an artery or in a vein. Depending on the location of the clot, this could cause a heart attack, a stroke, severe damage to other tissue, or death. A blood clot may occur within 2 weeks after you start taking the drug. About 25% (1 in 4) of patients taking the drug form an abnormal clot. Blood clots can occur in patients that do not have other known risk factors for forming clots. If you develop a blood clot, you will need to stop taking ponatinib. In some cases, emergency surgery could be needed to remove the clot and restore blood flow.